1. Field of the Invention
The present invention relates to a material for a negative electrode composed of a mixture of a non-carbon material and carbon material and a nonaqueous-electrolyte battery incorporating the material for a negative electrode. More particularly, the present invention relates to a material for a negative electrode exhibiting excellent resistance against cycle operations realized by specifying the particle size of each of the non-carbon material and the carbon material and a nonaqueous-electrolyte battery incorporate the foregoing material.
2. Description of the Related Art
Hitherto, a multiplicity of portable electronic apparatuses, such as camcoders, portable telephones and laptop computers have made their appearance in recent years. The size and weight of the electronic apparatuses have been required. Studies have energetically been performed to improve the energy density of the secondary battery which serves as the power source for the electronic apparatus. In particular, lithium-ion secondary batteries have been expected because the lithium-ion battery permits a considerably high energy density as compared with that realized by the conventional lead batteries and the nickel-cadmium batteries.
As the material of the negative electrode of the lithium-ion battery, a carbon material, such as non-graphitizable carbon or graphite, has widely been used. The reason for this lies in that the foregoing carbon material has a relatively large capacity and capable of realizing satisfactory resistance against cycle operations.
Since the capacity has been enlarged in recent years, the foregoing carbon materials suffer from unsatisfactory capacities. Therefore, a further improvement in the performance has been required. Hence it follows that studies of materials for the negative electrode, such as silicon and tin, exhibiting larger capacities have energetically been performed so as to be substituted for the conventional carbon materials.
The non-carbon material for the negative electrode suffers from excessive change in the volume of the active material thereof occurring when lithium is doped/dedoped. Therefore, excessive deterioration in the resistance against cycle operations takes place, causing application of the foregoing carbon material to the battery to be inhibited.